Oxytocin

Breast Feeding; Lactation; Milk, Human; Oxytocics; Pituitary Hormones, Posterior

FDA approved drugs -> Active ingredient

FDA approved drugs -> Active ingredient

Uterotonics

FDA approved animal drugs -> Active ingredient

Pharmaceuticals -> UK Veterinary Medicines Directorate List

294.98 Ų [M-H]- [CCS Type: DT; Method: single field calibrated with Agilent tune mix (Agilent)]

298.97 Ų [M-H]- [CCS Type: DT; Method: stepped-field]

297.9 Ų [M-H]-

Shows an activity of 450-500 USP units/mg when compared with USP posterior pituitary reference std

Oxytocin from beef and hog sources shows no difference in amino acid composition

This chemical does not meet GHS hazard criteria for 79.6% (39 of 49) of all reports.

Warning

H302 (10.2%): Harmful if swallowed [Warning Acute toxicity, oral]

P203, P264, P270, P280, P301+P317, P318, P330, P405, and P501 (click each P-code to see the statement)

Aggregated GHS information provided per 49 reports by companies from 11 notifications to the ECHA C&L Inventory. Each notification may be associated with multiple companies.

The Approved Drug Products with Therapeutic Equivalence Evaluations List identifies currently marketed prescription drug products, including oxytocin, approved on the basis of safety and effectiveness by FDA under sections 505 of the Federal Food, Drug, and Cosmetic Act.

The Generic Animal Drug and Patent Restoration act requires that each sponsor of an approved animal drug must submit to the FDA certain information regarding patents held for the animal drug or its method of use. The Act requires that this information, as well as a list of all animal drug products approved for safety and effectiveness, be made available to the public. Oxytocin is included on this list.

Oxytocin may be used as a uterine contractor to precipitate and accelerate normal parturition and postpartum evacuation of uterine debris. In surgery it may be used postoperatively following cesarean section to facilitate involution and resistance to the large inflow of blood. It will contract smooth muscle cells of the mammary gland for milk letdown if the udder is in proper physiological state. ... Federal law restricts this drug to use by or on the order of a licensed veterinarian.

Oxytocin injection appears to be compatible with most iv infusion fluids but is reported to be physically incompatible with fibrinolysin, norepinephrine bitartrate, prochlorperazine edisylate, and warfarin sodium. Oxytocin injection has also been reported to be incompatible with various other drugs, but the compatibility depends on several factors (eg, the concentration of the drugs, resulting pH, temperature). Specialized references should be consulted for more specific compatibility information.

Water spray, dry chemical, carbon dioxide, or foam as appropriate for surrounding fire and materials.

As with all fires, evacuate personnel to a safe area. Firefighters should use self-contained breathing equipment and protective clothing.

Store in tight container as defined in the USP-NF. This material should be handled and stored per label instructions to ensure product integrity.

Oxytocin injection should be stored at temperatures less than 15-25 °C but should not be frozen. Pitocin should be refrigerated at 2-8 °C but may be exposed to temperatures ranging from 15-25 °C for up to 30 days; Pitocin exposed to this latter temperature range for longer periods should be discarded.

SRP: Expired or waste pharmaceuticals shall carefully take into consideration applicable DEA, EPA, and FDA regulations. It is not appropriate to dispose by flushing the pharmaceutical down the toilet or discarding to trash. If possible return the pharmaceutical to the manufacturer for proper disposal being careful to properly label and securely package the material. Alternatively, the waste pharmaceutical shall be labeled, securely packaged and transported by a state licensed medical waste contractor to dispose by burial in a licensed hazardous or toxic waste landfill or incinerator.

SRP: At the time of review, regulatory criteria for small quantity disposal are subject to significant revision, however, household quantities of waste pharmaceuticals may be managed as follows: Mix with wet cat litter or coffee grounds, double bag in plastic, discard in trash.

This material is assumed to be combustible. As with all dry powders, it is advisable to ground mechanical equipment in contact with dry material to dissipate the potential buildup of static electricity.

As a general rule, when handling USP Reference Standards, avoid all contact and inhalation of dust, mists, and/or vapors associated with the material. Wash thoroughly after handling.

/Use/ safety goggles or glasses /and/ protect exposed skin.

Engineering controls such as exhaust ventilation are recommended.

Use a NIOSH-approved respirator, if it is determined to be necessary by an industrial hygiene survey involving air monitoring. In the event that a respirator is not required, an approved dust mask should be used.

Severe hypertension has been reported when oxytocin was given 3-4 hours following prophylactic administration of a vasoconstrictor in conjunction with caudal block anesthesia.

Cyclopropane anesthesia may modify oxytocin's cardiovascular effects, producing less pronounced tachycardia but more severe hypotension than occurs with oxytocin alone; maternal sinus bradycardia with abnormal atrioventricular rhythms has been noted when oxytocin was used concomitantly with cyclopropane anesthesia.

Oxytocin reportedly has delayed induction of thiopental anesthesia by producing venous spasm that caused peripheral pooling of thiopental; however, this interaction has not been conclusively established.

Common adverse reactions associated with oxytocin administration include erythema at the site of injection, intensified contractions, more frequent contractions, nausea, vomiting, stomach pain, and loss of appetite. Serious adverse effects that require monitoring after oxytocin administration include cardiac arrhythmias, seizures, anaphylaxis, confusion, hallucinations, severe blood pressure elevations, and blurred vision.

Samples of human milk obtained from lactating women in the early postpartum period were assayed for oxytocin concentrations by specific RIA, following extraction procedures with Florisil. Mean oxytocin concentrations in human milk at postpartum day 1 to 5 were 4.5 +/- 1.1, 4.7 +/- 1.1, 4.0 +/- 1.3, 3.2 +/- 0.4, 3.3 +/- 0.6 microunits/mL (+/- SE), respectively. Oxytocin levels in milk were significantly increased by nursing (3.1 +/- 0.6, 5.3 +/- 1.0 microunits/mL, respectively). 3H-oxytocin in human milk was stable even after incubation at 37 degrees C for 2 hours. The dilution curve for milk was parallel to the curve for the standard oxytocin. The chromatographic fraction of immunoreactive oxytocin was identical to that of 3H-oxytocin. 3H-oxytocin was administered to lactating rats. Radioactivity in the neonatal gastric contents and plasma were 12.8% and 4.4% of the counts in the maternal plasma. It was made clear that oxytocin is stable in milk and that oxytocin in maternal blood can be transferred to milk and then to neonates.

/HUMAN EXPOSURE STUDIES/ ... Thirty-eight healthy women scheduled for a surgical suction curettage with general anesthesia were enrolled /in this study/ to assess the effect of oxytocin on QT interval. General anesthesia was induced by propofol and maintained by either propofol (n = 18) or sevoflurane (n = 20). Electrocardiographic recordings were obtained before and at 1, 2, 3, and 5 minutes after a 10-U intravenous bolus of oxytocin. Intravenous oxytocin induced a pronounced QTc interval prolongation of 41 +/- 21 ms ( P < 0.0001), which was maximal 1 minute after administration. The QTc interval returned to control values 3 minutes after oxytocin bolus. Oxytocin bolus also induced an increase in heart rate of 19 +/- 10 beats/min and a significant decrease in systolic arterial pressure of 11 +/- 9 mm Hg (both P < 0.0001). The drug used to maintain anesthesia was not an independent factor of QT interval prolongation in ANOVA analysis. Oxytocin intravenous bolus induced a large and transient QTc interval prolongation, suggesting that it may lead to proarrhythmia in circumstances favoring QTc interval increase.

/HUMAN EXPOSURE STUDIES/ ... In humans, oxytocin has been found to enhance trust and the ability to interpret the emotions of others. It has been suggested that oxytocin may enhance facial processing by increasing focus on the eye region of human faces. In a double-blind, randomized, placebo-controlled, between-subject design, /investigators/ tracked the eye movements of 52 healthy male volunteers who were presented with 24 neutral human faces after intranasal administration of 24 IU oxytocin or placebo. Participants given oxytocin showed an increased number of fixations and total gaze time toward the eye region compared with placebo participants. Oxytocin increases gaze specifically toward the eye region of human faces. This may be one mechanism by which oxytocin enhances emotion recognition, interpersonal communication, and social approach behavior in humans. Findings suggest a possible role for oxytocin in the treatment of disorders characterized by eye-gaze avoidance and facial processing deficits.

/HUMAN EXPOSURE STUDIES/ The aim of the work was to compare labor courses, ways of delivery, condition of the newborns in spontaneous and oxytocin-related labors and to analyse the indications for oxytocin administration. 2198 full-term deliveries (pregnant women qualified for elective caesarean section were excluded from the study) at the Provincial Hospital in Przemys'l, Poland. Labors with the adjunctive oxytocin infusion--1102 women. Spontaneous labors (without oxytocin administration)--1096 women. The analysis of the compatibility of measured traits was carried out by the Chi-squared test (Chi2), p < 0.05 was assumed as statistically significant level. Indications for the oxytocin administration: secondary hypokinetic contractions of the uterus (642 labors--58.25%), premature rupture of membranes (176 labors - 15.97 %). Deliveries by caesarean section: 1. study group--187 women (16.97%). 2. control group--97 women (8.85%). Chi2 = 32.192; df = 1; p = 0.0000. Newborns after vaginal labors scored 7 or below according to the Apgar in the first minute after the delivery. 1. study group--35 newborns (8.7%); 2. control group--18 newborns (1.8%) Chi2 = 5.493; df = 1; p = 0.0190. Newborns hospitalized for over 48 hours: 1. study group--346 (31.39%); 2. control group--216 newborns (19.70%). Chi2 = 39.454; df = 1; p = 0.0000. Hypokinetic uterine contractions were the most frequent indication for oxytocin administration during labor. Oxytocin administration increases twice the risk of delivery by the caesarean section. Newborns after vaginal oxytocin-related labours scored 7 or below on the Apgar score in the first minute after the birth when compared to the newborns after spontaneous labor. Oxytocin administration during parturition elongates the time of newborns hospitalization.

/HUMAN EXPOSURE STUDIES/ Oxytocin (OT) effect on ghrelin-stimulated neuropeptide Y (NPY) secretion was evaluated in 12 normal men. Tests: ghrelin (1 ug/kg B.W. as an intravenous bolus); OT (2 mIU/min infusion); ghrelin plus OT; normal saline. Plasma NPY did not change during saline or OT infusions, whereas it showed a significant 29% increase vs baseline at 15 min after ghrelin injection. When OT was present, ghrelin-induced NPY increment was completely abolished. Results show that oxytocin modulates the NPY response to ghrelin, whereas it is unable to produce direct inhibitions of basal circulating NPY levels.

For more Human Toxicity Excerpts (Complete) data for Oxytocin (21 total), please visit the HSDB record page.

Drug Induced Liver Injury Rank (DILIrank 2.0)

Oxytocin

vNo-DILI-concern

0

No match

DOI:10.1016/j.drudis.2016.02.015

/LABORATORY ANIMALS: Developmental or Reproductive Toxicity/ The effects of oxytocin on fetal and placental growth and on maternal weight gain and accumulation of body fat were studied in ad libitum-fed and food-restricted (receiving 70% of the food intake of the ad libitum-fed group) pregnant rats. Further, a possible role of the IGF axis in mediating oxytocin-induced changes was assessed. Pregnant rats were injected subcutaneously once a day during gestational d 1-5 with saline or oxytocin (1 mg/kg). Ad libitum-fed oxytocin-treated pregnant rats had higher circulating levels of IGF-I, larger placentas, fetuses, and newborn pups and contained less body fat at the end of pregnancy. In food-restricted dams, oxytocin-treatment had no effect on fetal and placental growth. Additionally, food restriction attenuated the normal increase in IGF binding protein-3 protease proteolysis during pregnancy. The results show that oxytocin may affect maternal adaptations to pregnancy and stimulate fetal growth. /The authors/ suggest that this effect may be mediated by increased IGF-I in ad libitum-fed animals, whereas food restriction may block this effect by resulting in low levels of circulating IGF-I and by attenuating the pregnancy-associated increase in IGF binding protein-3 protease activity and, thereby, further compromise IGF bioavailability.

/LABORATORY ANIMALS: Developmental or Reproductive Toxicity/ ... Ten pregnant ewes received either saline solution (control, n = 5) or long-term administration of oxytocin (600 microU. kg-1. min-1) in 5-minute pulses every 20 minutes to the maternal jugular vein beginning at 96 days' gestation (n = 5). Maternal tracheal tubes, fetal carotid artery and jugular vein catheters, and electrocorticographic and electromyographic electrodes were placed with the animals under halothane general anesthesia at 122 days' gestation. At 131 days' gestation fetal hypoxemia was induced for 1 hour. Maternal and fetal arterial blood gas samples were obtained at 60, 15, and 5 minutes before the start of hypoxemia and at 5, 10, 20, 30, 40, 60, and 120 minutes after the start of hypoxemia. Baseline PO2 before hypoxemia was significantly lower and oxygen content was significantly higher in fetuses in the long-term oxytocin group than in control fetuses. At the end of hypoxemia the fetal pH, oxygen saturation, and oxygen content were significantly higher in the long-term oxytocin group than in the control group, although PO2 did not differ between groups. The fetal blood oxygen dissociation curve was shifted to the left in the long-term oxytocin group. During hypoxemia the absolute fetal blood pH was higher and the blood pH variation was lower in long-term oxytocin group than in the control group. Lower baseline and hypoxia-induced fetal plasma cortisol concentrations were observed in fetuses in the long-term oxytocin group than in fetuses of control ewes. Increased contracture frequency during a period of 35 days shifts the fetal oxygen dissociation curve toward the left and alters fetal response to acute hypoxemia.

/OTHER TOXICITY INFORMATION/ The objective was to characterize the urinary oxytocin (OT) system with the goal of using it as a biomarker for neurohypophyseal peptide secretion. We studied urinary OT secretion in mice under three conditions: (1) in OT gene deletion mice (OT -/-) which lack the ability to produce the peptide; (2) after arterial vascular infusion of OT and (3) after physiological stimulation with consumption of 2% sodium chloride. OT was measured by radioimmunoassay (RIA) and Surface-Enhanced Laser Desorption Ionization Time of Flight Mass Spectroscopy (SELDI TOF MS). In OT -/- mice (n=25), urinary OT levels were not detectable, while in OT +/+ mice (n=23) levels were 250.2+/-35.3 pg/mL. To evaluate blood/urine transfer, mice with chronic carotid arterial catheters were infused with saline or OT (5 or 20 pmol/min). Peak urine OT levels were 89+/-11.5 and 844+/-181 ng/mL in the low and high OT groups, respectively. Proteomic evaluation showed MS peaks, corresponding to OT ( approximately 1009 Da) and a related peptide ( approximately 1030 Da) with highest levels in mice infused with OT. Salt loading (5 days of 2% NaCl as drinking water) increased plasma osmolality (3.3%), increased plasma and urinary vasopressin (AVP), but caused no changes in OT. Thus, using non-invasive urine samples, we document that urinary OT and AVP can be used to monitor changes in peptide secretion. Urinary OT and AVP, as well as other urinary peptides, may provide a viable biomarker for peptide secretion and may be useful in clinical studies.

/SRP:/ Immediate first aid: Ensure that adequate decontamination has been carried out. If patient is not breathing, start artificial respiration, preferably with a demand valve resuscitator, bag-valve-mask device, or pocket mask, as trained. Perform CPR if necessary. Immediately flush contaminated eyes with gently flowing water. Do not induce vomiting. If vomiting occurs, lean patient forward or place on the left side (head-down position, if possible) to maintain an open airway and prevent aspiration. Keep patient quiet and maintain normal body temperature. Obtain medical attention. /Poisons A and B/

/SRP:/ Basic treatment: Establish a patent airway (oropharyngeal or nasopharyngeal airway, if needed). Suction if necessary. Watch for signs of respiratory insufficiency and assist ventilations if needed. Administer oxygen by nonrebreather mask at 10 to 15 L/min. Monitor for pulmonary edema and treat if necessary ... . Monitor for shock and treat if necessary ... . Anticipate seizures and treat if necessary ... . For eye contamination, flush eyes immediately with water. Irrigate each eye continuously with 0.9% saline (NS) during transport ... . Do not use emetics. For ingestion, rinse mouth and administer 5 mL/kg up to 200 mL of water for dilution if the patient can swallow, has a strong gag reflex, and does not drool ... . Cover skin burns with dry sterile dressings after decontamination ... . /Poisons A and B/

/SRP:/ Advanced treatment: Consider orotracheal or nasotracheal intubation for airway control in the patient who is unconscious, has severe pulmonary edema, or is in severe respiratory distress. Positive-pressure ventilation techniques with a bag valve mask device may be beneficial. Consider drug therapy for pulmonary edema ... . Consider administering a beta agonist such as albuterol for severe bronchospasm ... . Monitor cardiac rhythm and treat arrhythmias as necessary ... . Start IV administration of D5W /SRP: "To keep open", minimal flow rate/. Use 0.9% saline (NS) or lactated Ringer's if signs of hypovolemia are present. For hypotension with signs of hypovolemia, administer fluid cautiously. Watch for signs of fluid overload ... . Treat seizures with diazepam or lorazepam ... . Use proparacaine hydrochloride to assist eye irrigation ... . /Poisons A and B/

The Approved Drug Products with Therapeutic Equivalence Evaluations List identifies currently marketed prescription drug products, including oxytocin, approved on the basis of safety and effectiveness by FDA under sections 505 of the Federal Food, Drug, and Cosmetic Act.

The Generic Animal Drug and Patent Restoration act requires that each sponsor of an approved animal drug must submit to the FDA certain information regarding patents held for the animal drug or its method of use. The Act requires that this information, as well as a list of all animal drug products approved for safety and effectiveness, be made available to the public. Oxytocin is included on this list.

Oxytocin may be used as a uterine contractor to precipitate and accelerate normal parturition and postpartum evacuation of uterine debris. In surgery it may be used postoperatively following cesarean section to facilitate involution and resistance to the large inflow of blood. It will contract smooth muscle cells of the mammary gland for milk letdown if the udder is in proper physiological state. ... Federal law restricts this drug to use by or on the order of a licensed veterinarian.

H - Systemic hormonal preparations, excl. sex hormones and insulins

QH - Systemic hormonal preparations, excl. sex hormones and insulin

H01BB02

Oxytocin is a nonapeptide, pleiotropic hormone that exerts important physiological effects. It is most well known to stimulate parturition and lactation, but also has important physiological influences on metabolic and cardiovascular functions, sexual and maternal behaviour, pair bonding, social cognition, and fear conditioning. It is worth noting that oxytocin receptors are not limited to the reproductive system but can be found in many peripheral tissues and in central nervous system structures including the brain stem and amygdala.

Oxytocin plays a vital role in labour and delivery. The hormone is produced in the hypothalamus and is secreted from the paraventricular nucleus to the posterior pituitary where it is stored. It is then released in pulses during childbirth to induce uterine contractions. The concentration of oxytocin receptors on the myometrium increases significantly during pregnancy and reaches a peak in early labor. Activation of oxytocin receptors on the myometrium triggers a downstream cascade that leads to increased intracellular calcium in uterine myofibrils which strengthens and increases the frequency of uterine contractions. In humans, most hormones are regulated by negative feedback; however, oxytocin is one of the few that is regulated by positive feedback. The head of the fetus pushing on the cervix signals the release of oxytocin from the posterior pituitary of the mother. Oxytocin then travels to the uterus where it stimulates uterine contractions. The elicited uterine contractions will then stimulate the release of increasing amounts of oxytocin. This positive feedback loop will continue until parturition. Since exogenously administered and endogenously secreted oxytocin result in the same effects on the female reproductive system, synthetic oxytocin may be used in specific instances during the antepartum and postpartum period to induce or improve uterine contractions.

The pharmacologic and clinical properties of oxytocin are identical with those of naturally occurring oxytocin principle of the posterior lobe of pituitary. Oxytocin exerts a selective action on the smooth musculature of the uterus, particularly toward the end of pregnancy, during labor, and immediately following delivery. Oxytocin stimulates rhythmic contractions of the uterus, increases the frequency of existing contractions, and raises the tone of the uterine musculature.

Oxytocin indirectly stimulates contraction of uterine smooth muscle by increasing the sodium permeability of uterine myofibrils. High estrogen concentrations lower the threshold for uterine response to oxytocin. Uterine response to oxytocin increases with the duration of pregnancy and is greater in patients who are in labor than those not in labor; only very large doses elicit contractions in early pregnancy. Contractions produced in the term uterus by oxytocin are similar to those occurring during spontaneous labor. In the term uterus, oxytocin increases the amplitude and frequency of uterine contractions which in turn tend to decrease cervical activity producing dilation and effacement of the cervix and to transiently impede uterine blood flow.

Oxytocin contracts myoepithelial cells surrounding the alveoli of the breasts, forcing milk from the alveoli into the larger ducts and thus facilitating milk ejection. The drug possesses no galactopoietic properties.

Oxytocin produces vasodilation of vascular smooth muscle, increasing renal, coronary, and cerebral blood flow. Blood pressure is usually unchanged, but following iv administration of very large doses or undiluted solutions, blood pressure may decrease transiently, and tachycardia and an increase in cardiac output may be reflexly induced. Any initial fall in blood pressure is usually followed by a small but sustained increase in blood pressure. In contrast to vasopressin, oxytocin has minimal antidiuretic effects; however, water intoxication may occur when oxytocin is administered with an excessive volume of electrolyte-free iv fluids and/or at too rapid a rate.

For more Mechanism of Action (Complete) data for Oxytocin (15 total), please visit the HSDB record page.

The plasma half-life of oxytocin ranges from 1-6 minutes. The half-life is decreased in late pregnancy and during lactation.

Oxytocin has a plasma half-life of about 3 to 5 minutes.

Oxytocin is rapidly removed from the plasma by the liver and kidney. The enzyme oxytocinase is largely responsible for the metabolism and regulation of oxytocin levels in pregnancy and only a small percentage of the neurohormone is excreted in the urine unchanged. Oxytocinase activity increases throughout pregnancy and peaks in the plasma, placenta and uterus near term. The placenta is a key source of oxytocinase during gestation and produces increasing amounts of the enzyme in response to increasing levels of oxytocin produced by the mother. Oxytocinase activity is also expressed in mammary glands, heart, kidney, and the small intestine. Lower levels of activity can be found in the brain, spleen, liver, skeletal muscle, testes, and colon. The level of oxytocin degradation is negligible in non-pregnant women, men, and cord blood.

Oxytocinase, a circulating enzyme produced early in pregnancy, is also capable of inactivating the polypeptide.

During pregnancy ... "oxytocinase" ... is capable of inactivating oxytocin by cleavage of the 1-cysteine to 2-tyrosine peptide bond.

1JQS135EYN

OXYTOCIN

Physiologic Effects [PE] - Increased Uterine Smooth Muscle Contraction or Tone

Established Pharmacologic Class [EPC] - Oxytocic

Chemical Structure [CS] - Oxytocin

Oxytocin is an Oxytocic. The physiologic effect of oxytocin is by means of Increased Uterine Smooth Muscle Contraction or Tone.

Drugs that stimulate contraction of the myometrium. They are used to induce LABOR, OBSTETRIC at term, to prevent or control postpartum or postabortion hemorrhage, and to assess fetal status in high risk pregnancies. They may also be used alone or with other drugs to induce abortions (ABORTIFACIENTS). Oxytocics used clinically include the neurohypophyseal hormone OXYTOCIN and certain prostaglandins and ergot alkaloids. (From AMA Drug Evaluations, 1994, p1157)

Oxytocin is administered parenterally and is fully bioavailable. It takes approximately 40 minutes for oxytocin to reach steady-state concentrations in the plasma after parenteral administration.

The enzyme oxytocinase is largely responsible for the metabolism and regulation of oxytocin levels in pregnancy; only a small percentage of the neurohormone is excreted in the urine unchanged.

In a study that observed 10 women who were given oxytocin to induce labor, the mean metabolic clearance rate was 7.87 mL/min.

Oxytocin is destroyed by chymotrypsin in the GI tract. Uterine response occurs almost immediately and subsides within 1 hour following iv administration of oxytocin. Following im injection of the drug, uterine response occurs within 3-5 minutes and persists for 2-3 hours. Following intranasal application of 10-20 units of oxytocin (nasal preparations are no longer commercially available in the US), contractions of myoepithelial tissue surrounding the alveoli of the breasts begin within a few minutes and continue for 20 minutes; iv oxytocin produces the same effect with a dose of 100-200 milliunits.

Like vasopressin, oxytocin is distributed throughout the extracellular fluid. Small amounts of oxytocin probably reach the fetal circulation.

It is not known whether this drug is excreted in human milk.

MEDICATION

MEDICATION (Vet)

Oxytocin injection, USP ... contains 10 USP units per mL and may be administered iv or im. All commercial preparations are now synthetic.

... injection, USP

Each mL of posterior pituitary injection NF possesses oxytocic activity equivalent to 10 USP posterior pituitary units (permissible range, 8.5-12 units) ... /Posterior pituitary/

The hypotensive response of the chicken is the basis for the USP bioassay for oxytocin.